TW201430162A - Method for producing pyrolytic boron nitride coated carbon base material - Google Patents

Abstract

The invention provides a method for producing a pyrolytic boron nitride coated carbon base material which can inhibit peeling and the like between a pyrolytic boron nitride coated film and a carbon base material through a simple method. The invention is the method for producing the pyrolytic boron nitride coated carbon base material by using a pyrolytic boron nitride to coat a portion of or all of the carbon base material and is characterized in that a surface roughness of the carbon base material is preferably adjusted to 0.5 μ m or more and less than 7.0 μ m based on a calculation average roughness defined in JIS B 0601-2001, and a thermal expansion coefficient of the coated film comes close to a thermal expansion coefficient of the carbon base material.

Description

Method for producing thermal decomposition boron nitride coated carbonaceous substrate

The present invention relates to a method for producing a carbon substrate coated with pyrolytic boron nitride, which is generally used for a heater used in, for example, a semiconductor and a solar cell manufacturing apparatus ( Heater), jig, etc.

The pyrolytic boron nitride is prepared by a CVD method and is a material having high insulation, high heat resistance, and flexibility. The structure is a hexagonal system similar to graphite, and the physical property values are significantly different in the a direction parallel to the growth surface and the c direction perpendicular to the growth surface. In particular, the coefficient of thermal expansion is about 3.0 × 10 ^-6 [1/°C] in the a direction and about 30 × 10 ^-6 [1/°C] in the c direction, and has a difference of about 10 times.

When the pyrolytic boron nitride having such a physical property value is coated on the carbon substrate, if there is no difference in the thermal expansion coefficient between the carbon substrate and the coating film, peeling between the carbon substrate and the coating film can be suppressed. Therefore, as the carbon substrate, a material whose thermal expansion coefficient is close to that of the pyrolytic boron nitride is usually selected.

In addition, in the case of a carbon substrate, a molding material, an extruded material, and a CIP are usually used. However, when a block of a molding material, a CIP material, or the like is prepared, the influence of uncertain factors in the manufacturing steps such as mixing, molding, and baking cannot be avoided, and thus, it is actually manufactured. There is no difference in physical property values between batches of blanks, and this problem is no exception to the coefficient of thermal expansion. As described above, if the thermal expansion coefficient of each batch of the carbon substrate is different, even if the film quality of the pyrolytic boron nitride film can be uniformly formed, the difference in thermal expansion coefficient between the carbon substrate and the coating film after the production is made , deformation or peeling will also occur.

As a measure against the peeling, Patent Document 1 describes a coating method in which the surface roughness of the carbon substrate is increased and the peeling is avoided by the anchoring action. However, this coating method has a problem in that peeling cannot be suppressed when a substrate having a large difference in expansion ratio from the pyrolytic boron nitride film is used because of a difference in thermal expansion coefficient of the carbon substrate.

Further, Patent Document 2 describes a method of forming a crack-free coating film on a carbon substrate by coating a pyrolytic boron nitride film having a low thermal expansion coefficient close to that of a carbon substrate. However, this coating method also has a problem that peeling occurs when there is a difference in thermal expansion coefficient of the carbon substrate and a difference in thermal expansion coefficient from the pyrolytic boron nitride film. Patent Document 2 does not describe any method of adjusting the difference in the expansion ratio.

In summary, the coating method described in the prior art documents has a problem in that although the thermal expansion coefficients of each batch of carbon substrates are different, the thermal expansion coefficients of the pyrolytic boron nitride film are not adjusted to Since the coefficient of thermal expansion of the carbon substrate is matched, peeling occurs when the difference in expansion ratio is large.

[Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. Hei 3-10076

[Patent Document 2] Japanese Patent No. 2729289

Therefore, the inventors of the present invention can suppress the peeling between the carbon substrate and the coating film by a relatively simple method even when a carbon substrate block having a difference in thermal expansion coefficient per lot is used. As a result of intensive studies, it has been found that when the material to be coated is anisotropic pyrolytic boron nitride having different thermal expansion coefficients in the a direction and the c direction, the so-called disorder layer structure which is an alignment disorder At the time, the contribution of the expansion coefficient in the c-axis direction is increased, and the expansion coefficient in the a direction parallel to the growth surface tends to change.

The inventors have further obtained the following findings to facilitate the present invention. That is, since the disorder of the alignment of the a-axis and the c-axis of the pyrolytic boron nitride is also affected by the change in the surface roughness of the carbon substrate, if the surface roughness of the substrate is changed, the thermal nitridation is performed. The alignment of the a-axis and the c-axis of the boron coating film is disturbed, and as a result, the thermal expansion coefficient of the coating film can be changed by such an alignment disorder.

That is, an object of the present invention is to provide a method for producing a pyrolytic boron nitride-coated carbon substrate, which has a thermal expansion coefficient close to that of a carbon substrate by a simple method of adjusting the surface roughness of the carbon substrate. Thermal expansion coefficient Inhibition of peeling and the like.

The present invention relates to a method for producing a pyrolytic boron nitride-coated carbon substrate, which comprises coating a part or all of a carbon substrate with pyrolytic boron nitride, wherein the heat is controlled by adjusting a surface roughness of the carbon substrate. The thermal expansion coefficient of the boron nitride coating film.

Further, the surface roughness of the carbon substrate of the present invention is preferably adjusted to 0.5 μm or more and less than 7.0 μm in terms of arithmetic mean roughness as defined in JIS B 0601-2001; and the above-described pyrolytic boron nitride coating film is preferably used. The peak intensity ratio I(002)/I(100) calculated by the peak intensity I(002) derived from the crystal plane (002) and the peak intensity I(100) derived from the crystal plane (100) It is 10 or more and less than 500.

According to the present invention, by adjusting the surface roughness of the carbon substrate, the thermal expansion coefficient of the pyrolytic boron nitride coating film can be controlled to be close to the thermal expansion coefficient of the carbon substrate, so that the difference in thermal expansion coefficient can be suppressed by a relatively simple method. The peeling between the coating film and the carbon substrate causes the bending, deformation, and warpage of the pyrolytic boron nitride-coated carbon substrate.

1‧‧‧Heat heater consisting of carbon substrate

2‧‧‧Electrical connection of the heater

Fig. 1 is a graph showing the relationship between the surface roughness of a carbon substrate and the thermal expansion coefficient of a pyrolytic boron nitride coating film.

Figure 2 is a graph showing the surface roughness of a carbon substrate and the peak intensity of a pyrolytic boron nitride coating film. A graph of the relationship between degrees.

3 is a view showing a relationship between a peak intensity ratio and a thermal expansion coefficient of a pyrolytic boron nitride coating film.

4 is a view showing an outline of a heater in which a carbon substrate is coated with pyrolytic boron nitride.

Hereinafter, an embodiment of the present invention will be specifically described. First, an experimental example that facilitates the present invention will be described.

<Experimental example>

In the experimental example, a total of 8 kinds of carbon substrates (isotropic graphite materials) of □50×3 mm from A-1 to D-2 were prepared, and these samples were individually adjusted to Table 1 by sand blasting treatment. The surface roughness shown. The blasting treatment was carried out using PNEUMA-BLASTER SG-5A manufactured by Fujisawa Seisakusho Co., Ltd., and the surface treatment was carried out at a spray pressure of 0.4, 0.7, 1.0, 1.5 MPa using FUJI RANDOM WA (alumina) #60 abrasive grains manufactured by Fujifilm Co., Ltd. The surface roughness of these samples was measured by SURFCORDER SEF580-M50, a surface roughness tester manufactured by Kosaka Research Institute. Then, a sample of eight kinds of carbon substrates which were surface-treated separately was placed in a vacuum furnace, and 150 μm of pyrolytic nitrogen was respectively applied to the carbon substrate by passing BCl ₃ and NH ₃ gas at 1800 ° C and 50 Pa. Boron film surface coating. Thereafter, the pyrolytic boron nitride coating film was peeled off from the eight kinds of samples coated as described above, and X-ray diffraction and thermal expansion coefficient α _{2 were} measured for each of the coating films. The X-ray diffraction at this time was obtained by Rigaku Corporation's X-ray diffraction RINT-2500 VHF at a tube voltage of 30 kV, a tube current of 30 mA, a scanning speed of 6.0 °/min, a sampling width of 0.05 °, and 2 θ = 20 to 60. Under the conditions of °.

In addition, the coefficient of thermal expansion was measured using a ULVAC vacuum DL7000 thermo-dilatometer at a temperature of 50 to 800 °C.

Table 1 shows the spray pressure, surface roughness of the surface treatment of the above eight samples, the peak intensity I (002) derived from the X-ray diffraction crystal plane (002) obtained from the experiment, and the crystal plane derived from the crystal plane. (100) The peak intensity ratio I (002) / I (100) obtained from the peak intensity I (100) data, and the value of the thermal expansion coefficient α ₂ of the coating film obtained by the experiment.

2 shows the relationship between the surface roughness of the carbon substrate and the peak intensity ratio of the coating film based on the numerical values of Table 1, and FIG. 3 shows the relationship between the peak intensity ratio of the coating film and the thermal expansion coefficient α ₂ . 2 and 3, the surface roughness of the carbon substrate and the peak intensity ratio of the coating film and the peak intensity ratio and the thermal expansion coefficient α ₂ have a certain regular relationship.

That is, according to Fig. 2, when the surface roughness of the carbon substrate is changed, the value of the peak intensity ratio of the coating film tends to decrease regularly with the change; on the other hand, according to Fig. 3, if the peak intensity is When the value of the ratio is small, the coefficient of thermal expansion of the coating film tends to increase with the change. Therefore, if the relationship between the surface roughness of the carbon substrate and the thermal expansion coefficient α ₂ of the coating film is shown based on these measurement results, it is as shown in FIG. 1 . It is clearly illustrated from Fig. 1 that as the surface roughness increases, the value of the coefficient of thermal expansion α ₂ also tends to increase regularly.

Therefore, the inventors of the present invention have focused on such a regular tendency, and have obtained the knowledge that the peak intensity ratio of the coating film and the thermal expansion coefficient α ₂ can be changed as long as the surface roughness of the carbon substrate is changed, thereby contributing to the present invention. . Therefore, according to the above findings, the present invention adjusts the surface roughness of the carbon substrate before the coating treatment to control the thermal expansion coefficient α _{2 of the} coated pyrolytic boron nitride film.

In the present invention, when the surface roughness of the carbon substrate is adjusted, it is preferably adjusted to an arithmetic mean roughness meter defined by JIS B 0601-2001 to be 0.5 μm or more and less than 7.0 μm, more preferably 2.0 μm or more and less than 5.0 μm. When the surface roughness is less than the lower limit of 0.5 μm, the thermal expansion coefficient of the substrate and the coating film can be made close to each other. However, since the anchoring effect on the surface of the carbon substrate is small, the coating film is easily peeled off, which is not preferable. In addition, when the surface roughness is greater than the upper limit of 7.0 μm, the possibility of forming a damaged layer on the surface of the carbon substrate is increased because the injection pressure for increasing the surface roughness to 7.0 μm or more is excessive, which is not preferable. As a method of adjusting the surface roughness, a sandblasting treatment, a sandpaper polishing treatment, an etching treatment, or the like can be employed.

Further, as shown in FIG. 3, the present invention can adjust the orientation of the pyroconductivity boron nitride film by adjusting the alignment property so that the peak intensity ratio I(002)/I(100) is in the range of 10 or more and less than 500. The coefficient of thermal expansion α ₂ .

In the production of the carbon substrate of the present invention, the thickness of the pyrolytic boron nitride film to be coated is preferably 50 μm or more and 300 μm or less. When the thickness of the coating film is thinner than 50 μm, a corrosive gas or the like diffuses in the coating film and easily reacts with the carbon substrate of the substrate, which is not preferable. In addition, when it is thicker than 300 μm, the residual stress at the interface with the coating film and the carbon substrate becomes large, and it is easy to peel off, which is not preferable.

Further, in the production of a carbon substrate, a carbon substrate produced by forming an isotropic CIP is often used. The coefficient of thermal expansion of such an isotropic carbon substrate depends on the production method thereof, but is about 3.0×10 ^-6 to 8.0. ×10 ^-6 [1/°C] range. The thermal expansion coefficient α _{2 of the} pyrolytic boron nitride coating film coated on the carbon substrate is generally in the range of about 2.5×10 ^-6 to 4.0×10 ^-6 [1/° C], and therefore, in carrying out the invention In the production method, referring to the values of these thermal expansion coefficients, a carbon substrate having a thermal expansion coefficient close to each other is preferable.

Example 1

Next, an embodiment of the present invention will be described in detail. In Example 1, a carbon substrate having a thermal expansion coefficient of 3.5 × 10 ^-6 [1/°C] was prepared, and the surface roughness was adjusted to 3.9 μm, and the surface of the pyrolytic boron nitride film similar to the above experimental example was applied. coating. The pyrolytic boron nitride coating film was peeled off from the carbon substrate after the coating, and the thermal expansion coefficient α _{2 of the} coating film was measured and found to be 3.6 × 10 ^-6 [1/°C]. Since this α ₂ value is a value which is quite close to the thermal expansion coefficient of the carbon substrate of 3.5 × 10 ^-6 [1/°C], this Example 1 verified the method of the present invention.

Example 2

Next, in order to confirm whether the manufacturing method of the present invention is effective in suppressing peeling or the like, six kinds of samples of E to J are prepared and carried out. In the second embodiment, the heater 1 schematically shown in Fig. 4 is used as a carbon substrate. The electrode connection portion 2 is provided at both ends of the six types of heaters 1, and has a shape of a total length of 600 mm, a width of 20 mm, and a thickness of 5 mm. Table 2 shows the values of the surface roughness and the coefficient of thermal expansion α1 of each of the six samples.

In Example 2, in order to measure the thermal expansion coefficient α _{2 of the} coating film after peeling off the coating film, a dummy sample of each sample was prepared in addition to the six kinds of samples. Each of the dummy samples was adjusted to be the same as the physical property values of the six samples, and placed in a vacuum furnace together with each sample. Then, a surface coating of a 150 μm pyrolytic boron nitride film was applied to the surface of the substrate of the sample heater 1 and the dummy sample heater 1 through BCl ₃ and NH ₃ gas at 1800 ° C and 50 Pa. After the surface coating, the pyrolytic boron nitride coating film was peeled off from the base material of each of the dummy samples, and the same X-ray diffraction and thermal expansion coefficient α ₂ as in Example 1 were measured for the coating film, and the measurement results were measured. Shown in Table 2.

On the other hand, in the heater 1 of each of the samples E to J, the coating film adhering to the electrode connecting portion 2 was removed, and after the power supply was connected to both ends, the gas was applied in an ammonia gas atmosphere at room temperature to 1400 ° C. In the heat cycle test, the samples E and J were peeled off, and no peeling was observed in the other samples, and good results were obtained. The results are shown in Table 2 above.

The reason for the peeling of the samples E and J was examined. The sample E was considered to be because the surface roughness was small and the anchoring effect was small, so that peeling occurred. On the other hand, the sample J is considered to have a surface roughness larger than the upper limit of 7.5 μm, and an excessive load force acts on the surface of the carbon substrate to form a damaged layer, and the surface particles fall off to cause peeling.

As described above, according to the present invention, when a pyrolytic boron nitride-coated carbon substrate for a heater, a jig or the like is produced, even if a carbon substrate obtained from each carbon material manufacturer has a difference in thermal expansion coefficient, The orientation and thermal expansion coefficient of the pyrolytic boron nitride coating film can be controlled by adjusting the surface roughness of the obtained carbon substrate in advance, because the coefficient of thermal expansion of the coated coating film and the carbon substrate can be reduced. Since the difference is made, it is possible to suppress peeling, deformation, and the like caused by the difference in thermal expansion coefficients of both.

Claims (3)

A method for producing a pyrolytic boron nitride-coated carbon substrate, wherein a part or all of the carbon substrate is coated with pyrolytic boron nitride, wherein the thermal nitriding is controlled by adjusting a surface roughness of the carbon substrate The coefficient of thermal expansion of the boron coating film. The method for producing a boron nitride-coated carbon substrate according to the first aspect of the invention, wherein the surface roughness of the carbon substrate is adjusted to 0.5 μm by an arithmetic mean roughness meter defined in JIS B 0601-2001. Above and less than 7.0 μm. The method for producing a pyrolytic boron nitride-coated carbon substrate according to the first or second aspect of the invention, wherein, in the pyrolytic boron nitride coating film, the transmission is derived from a crystal plane (002) The peak intensity I (002) and the peak intensity ratio I (100) calculated from the peak intensity I (100) of the crystal plane (100) are 10 or more and less than 500.